ECCENTRIC OVERLOAD IN FLYWHEEL DEVICES
Strength training has evolved with the use of flywheel devices, which provide variable resistance throughout the movement. One of the main advantages of these devices is the ability to induce eccentric overload, which is crucial for enhancing strength and preventing injuries. However, how can we ensure that we are truly achieving eccentric overload? In this post, we will explore what eccentric overload is and how to measure it accurately in flywheel devices.
What is eccentric overload?
Eccentric overload occurs when force production in the eccentric phase of movement exceeds that in the concentric phase (Muñoz-López et al., 2023). Although, it can be as well monitored with power, as we will discuss later. This phenomenon has been shown to be critical for enhancing maximum strength and neuromuscular efficiency in elite athletes (Nuñez et al., 2019). In flywheel devices, this can be achieved by implementing specific strategies, such as delaying the braking action or adjusting the device’s moment of inertia. Studies have shown that eccentric overload is key to improving maximum strength, speed, and deceleration ability in athletes (Beato et al., 2024).
Figure 1. The figure illustrates the eccentric overload definition. It shows three repetitions, where angular speed increases towards the end of the concentric phase, decreasing during the eccentric phase. The first three repetitions show eccentric overload, measured with a force plate in the peak force. However, when power is measured, we can observe that the first repetition shows no eccentric overload, because the peak is higher during the concentric phase.
However, it is not always automatically achieved when using inertial devices, which is why proper monitoring is necessary. Studies indicate that eccentric overload in flywheel devices can be achieved by modifying the inertial resistance and braking technique. However, in order to maximize its benefits, it is essential to measure and control these variables in every repetition.
Techniques to Measure Eccentric Overload in Flywheel Devices
Key Variables for Eccentric Overload Measurement
- Peak power and peak velocity: Most reliable indicators, as they typically show higher eccentric than concentric outputs (Muñoz-López et al., 2023; Núñez et al., 2020).
- Angular speed and angular acceleration: Also effective markers, especially when using lower moments of inertia.
Flywheel Device Type Selection
- Cylindrical shaft devices: Tend to generate higher peak eccentric force, making them more effective for eccentric overload (Núñez et al., 2020).
- Conical shaft devices: Allow for greater acceleration during the concentric phase, which may reduce eccentric overload effects.
Optimal Moments of Inertia for Eccentric Overload
- Lower inertia values (0.025–0.1 kg·m²): Enable higher eccentric velocities and power outputs, maximizing eccentric overload (Sabido et al., 2018; Muñoz-López et al., 2021).
- Higher inertia values: Tend to decrease movement speed, limiting the potential for eccentric overload.
Practical Recommendations
- Monitor peak power, peak angular velocity, and acceleration to track eccentric overload.
- Prefer cylindrical shaft flywheels to enhance eccentric force production.
- Select moments of inertia below 0.1 kg·m² for optimal eccentric loading.
- Implement proper braking strategies to maximize the eccentric stimulus.
Figure 2. The figure illustrates how to effectively monitor the eccentric overload using SmartCoach devices. Data belongs to a squat exercise executed with a cylindrical shaft flywheel device. The yellow bar shows the concentric peak power. If peak power during the eccentric phase is higher than the desired eccentric overload objective (in this example, 30% of eccentric overload), the software returns a blue repetition. If the peak power is within the objective range, the repetition is green. In case of a higher eccentric overload, it turns into red. In practical terms, the subject here was able to achieve the desired eccentric overload only in 4 repetitions.
Conclusion
Eccentric overload is a fundamental principle in optimizing strength training with flywheel devices. However, measurement and control are essential to ensure the desired stimulus is being achieved. Technologies like SmartCoach provide advanced tools to evaluate the eccentric/concentric ratio in real time and optimize each training repetition. If you want to enhance your performance and prevent injuries through eccentric training, consider implementing an appropriate monitoring system in your routine.
References
- Beato, M., de Keijzer, K. L., Muñoz-López, A., Raya-González, J., Pozzo, M., & Alkner, B. A. (2024). Current guidelines for the implementation of flywheel resistance training technology in sports: A consensus statement. Sports Medicine. https://doi.org/10.1007/s40279-023-01979-x.
- Muñoz-López, A., Nakamura, F. Y., & Beato, M. (2023). Eccentric overload differences between loads and training variables on flywheel training. Biology of Sport, 40(4), 1151–1158. https://doi.org/10.5114/biolsport.2023.122483.
- Muñoz-López, A., de Souza Fonseca, F., Ramírez-Campillo, R., Gantois, P., Núñez, F. J., & Nakamura, F. Y. (2021). The use of real-time monitoring during flywheel resistance training programmes: How can we measure eccentric overload? A systematic review and meta-analysis. Biology of Sport, 38(4), 639–652. https://doi.org/10.5114/biolsport.2021.101602.
- Núñez, F. J., Galiano, C., Muñoz-López, A., & Floria, P. (2020). Is possible an eccentric overload in a rotary inertia device? Comparison of force profile in a cylinder-shaped and a cone-shaped axis devices. Journal of Sports Sciences, 38(4), 1–10. https://doi.org/10.1080/02640414.2020.1754111.
- Núñez, F. J., de Hoyo, M., Muñoz-López, A., Sañudo, B., Otero-Esquina, C., Sánchez, H., & Gonzalo-Skok, O. (2019). Eccentric-concentric ratio: A key factor for defining strength training in soccer. International Journal of Sports Medicine. https://doi.org/10.1055/a-0977-5478.
- Sabido, R., Hernández-Davó, J. L., & Pereyra-Gerber, G. T. (2018). Influence of different inertial loads on basic training variables during the flywheel squat exercise. International Journal of Sports Physiology and Performance. https://doi.org/10.1123/ijspp.2017-0282.
